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Interpretive Summary: The effects of nitrogen (N) fertilizer source on nitrous oxide (N2O) emissions from a strip-till (ST), irrigated continuous corn field in 2009 near Fort Collins, CO was evaluated. Nitrous oxide emissions were monitored from plots receiving six different inorganic N fertilizer sources (urea, ESN®, SuperU®, UAN, UAN+AgrotainPlus®, UAN+Nfusion®) at a rate of 202 kg N/ha surface band applied near the corn row and watered (19 mm irrigation water) into the soil the day after application. A subsurface band application of ESN® was included as well as a blank treatment (no N applied) within the N source plot. A check plot (no N applied) located in a separate plot was also included. All N sources had significantly lower growing season N2O emissions than dry granular urea. Cumulative increases in daily N2O fluxes were more rapid for urea and UAN following N application than for the other N sources. The enhanced efficiency fertilizers (polymer-coated, stabilized, and slow release) sources showed potential for reducing N2O emissions in a strip-tilled, irrigated corn system during the 2009 growing season. Corn grain yields in 2009 were not significantly different between N sources receiving 202 kg N/ha. These first year results under strip-till conditions indicate N sources need to be evaluated further to confirm their potential value in reducing N2O emissions in irrigated cropping systems.

Technical Abstract: We evaluated the effects of nitrogen (N) source on nitrous oxide (N2O) emissions from a strip-till (ST), irrigated continuous corn field in 2009 near Fort Collins, CO. Emissions were monitored from plots receiving six different inorganic N fertilizer sources (urea, ESN®1, SuperU®, UAN, UAN+AgrotainPlus®, UAN+Nfusion®) at a rate of 202 kg N/ha surface band applied near the corn row and watered (19 mm irrigation water) into the soil the day after application. A subsurface band application of ESN® was also included. A check plot (no N fertilizer applied since 2000) located in a separate plot and a blank treatment (no N applied) located within the N source plot were also included. All N treatments were located in plots that were previously in a conventional plow tillage continuous corn (CT-CC) system in 2007-2008, but strip-tilled in 2009, that had received 202 kg N/ha as a polymer-coated urea, ESN®. Nitrous oxide fluxes were measured during the growing season using static, vented chambers for gas sample collection, one to three times per week, and analyzed with a gas chromatograph. All N sources had significantly lower growing season N2O emissions than dry granular urea. Cumulative increases in daily N2O fluxes were more rapid for urea and UAN than the other N sources following N fertilizer application. The enhanced efficiency fertilizers (polymer-coated, stabilized, and slow release) sources showed potential for reducing N2O emissions in a strip-tilled, irrigated corn system during the 2009 growing season. Corn grain yields in 2009 were not significantly different between N sources receiving 202 kg N/ha. These first year results under strip-till conditions indicate N sources need to be evaluated further to confirm their value in reducing N2O emissions in irrigated cropping systems.